This invention concerns ion exchangers and, more particularly, this invention concerns inorganic anion exchangers, a process for their preparation, and their use. It is directed to a novel composition and a method for controlling colorant migration in a liquid by means of an anion exchanger material. More particularly, this invention relates to a composition and method for use in laundering clothes which controls and/or eliminates colorants in the water and allows differently colored clothes to be laundered together.
In the past, noncolorfast fabrics or substrates or items capable of producing colorants have been laundered with substrates or fabrics having different colors. This condition frequently resulted in colorants migrating from the noncolorfast item into the water and then onto differently colored fabrics or substrates resulting in undesirable coloring.
The use of anion exchange material for the removal of color from alkaline solution is described by Gustafson in U.S. Pat. No. 2,561,595. U.S. Pat. No. 3,002,932 describes several noncrystalline inorganic anion exchangers consisting essentially of hydrated oxides of pairs of elements selected from the group consisting of aluminum, silicon, titanium, zinc, and zirconium. These compositions are prepared by coprecipitating the hydrates of the combination of the oxides of the elements referred to above in an aqueous medium. The coprecipitation is carried out by gradually adding a base to an acid below a pH of 5 to bring the aqueous solution to a pH of about 5 to 7. The aqueous mixture is dried below about 150.degree. C., followed by washing the dried mixed hydrated oxide with water, and again finally drying the mixture at below about 150.degree. C.
In a paper by E. J. Duwell and J. W. Shepard, "The Preparation and Properties of Some Synthetic Inorganic Anion Exchangers", Journal of Physical Chemistry, Vol. 63, December, pp. 2044-47, (1959), various amorphous inorganic anion exchangers are described. The paper describes a method for preparing an amorphous Zn(OH).sub.2 exchanger and Al(OH).sub.3 exchanger. The amorphous exchangers are prepared by coprecipitating cations of higher valence with aluminum and zinc hydroxide in slightly acidic solutions to form a gel. The gels are then dried to form white, finely divided amorphous powders of Al(OH).sub.3 and Zn(OH).sub.2.
The prior art above reports that x-ray diffraction analysis of the exchangers described indicates that the exchangers are noncrystalline or amorphous. In addition, the prior art teaches that when the exchangers are dehydrated at 150.degree. C. or higher, a crystalline product is formed and the product loses its anion exchange capacity.
Contrary to the teachings in the above prior art, the present invention provides novel inorganic mixed metal hydroxides and mixed metal hydrated oxides having a substantially crystalline structure, as shown by x-ray diffraction patterns, and exhibiting anion exchange properties. A method by which these inorganic mixed metal hydroxides and mixed metal hydrated oxides may be prepared is also shown.
One aspect of the present invention is an anion exchange material comprising a substantially crystalline material exhibiting anion exchange properties represented by the formula: EQU [M.sup.a.sub.1--x Q.sub.x.sup.a+1 O.sub.y (OH).sub.z ] (A.sup.-1).sub.d (A.sup.-2).sub.e (A.sup.-3).sub.f (A.sup.-4).sub.g.nH.sub.2 O (I)
where M is a metal element or elements each with a positive valence of a; Q is a metal element or elements each with a positive valence of a+l; a is 2, 3, 4, or 5; A.sup.-1, A.sup.31 2, A.sup.-3, and A.sup.-4 are each one or more exchangeable anions each having a negative valence of 1, 2, 3, and 4, respectively; x is 0 &lt;x &lt;0.5; and n, y, z, d, e, f, and g are real numbers greater than or equal to zero and satisfy the following: EQU 2y+z=a; y&lt;z EQU 0&lt;d+2e+3f+4g.ltoreq.x EQU 0.ltoreq.n.ltoreq.10
provided that when y=0, a is not equal to 2.
Another aspect of the present invention is a process of preparing the compositions of the above formula (I) which comprise coprecipitating in an aqueous medium, at a constant acidic pH, inorganic mixed metal hydroxides or hydrated mixed metal oxides of metal elements, said mixed metal hydroxide or hydrated mixed metal oxides having a substantially crystalline lattice structure as shown by x-ray diffraction patterns and exhibiting anion exchange properties at temperatures up to 150.degree. C.
A further aspect of this invention is a method of controlling colorant migration in a liquid comprising contacting said liquid with a sufficient amount of the above-described composition.